Forks for agricultural, horticultural and like purposes



"Oct. 10, 1967 E. H. MILLS 3,34 8

FORKS FOR AGRICULTURAL, HORTICULTURAL AND LIKE PURPOSES Filed Dec. 28, 1964 f J I /6 /5/ mvsm'oa. r J. EDMUND HARRY MILLS United States Patent 3,345,887 FORKS FOR AGRICULTURAL, HORTICULTURAL AND LIKE PURPOSES Edmund Harry Mills, Sheffield, Yorkshire, England, assignor to William Mills & Co. (Shefiield) Limited, a company of Great Britain and Northern Ireland Filed Dec. 28, 1964, Ser. No. 421,262 Claims priority, application Great Britain, Dec. 31, 1963, 51,262/ 63 3 Claims. (Cl. 76-111) This invention relates to the manufacture of forks for agricultural, horticultural and like purposes.

It has long been recognized that there are both advantages, and a demand, for such implements to be made of stainless steel, but the present methods of manufacture of such implements from ordinary steel are not adapted for production from stainless steel which suffers degradation such as air cracking and loss of strength, if not actual fracture, under the working stresses and conditions to which the metal is thereby subjected. In consequence, the present known practical method of production from stainless steel is by casting, and subsequent finishing, which method can never produce a product of the same quality, appearance and strength compared with an ordinary (non-stainless) steel fork made by present known methods of blanking and rolling.

With present known methods of production, the prongs, formed (at a very early stage) by blanking and slitting from a billet, have to be bent and re-bent several times so that each prong in turn can be presented individually to rollers for shaping whilst the others are bent away clear of such rollers, and for each such operation the billet has to be re-heated to the required known working temperature of the order of 900 C. to 1000 C. As previously stated, as has been found in practice stainless steel cannot withstand such treatment without fracture or serious degradation.

The present invention is based upon the appreciation that failure of attempts to apply existing methods to stainless steel is due, not only to the severity of bending and rebending aforesaid of the prongs, but also to the relatively large and frequent changes in temperature which result from the frequent reheating between the several phases of manipulation, during which latter the prongs especially cool very rapidly, owing to their length and small cross section. Present methods may involve as many as 9 or more heating and re-heating operations during which the temperature of the prongs may vary between each reheating from an initial working temperature as aforesaid somewhere between 900 C. and 1000 C. to as low as black heat or about 500 C. especially at the extremity of the prongs.

The object of the present invention is an improved method of manufacture of such implements involving fewer heating and re-heating operations and smaller temperature changes between such operations, particularly in the prongs, so that stainless steel may be employed using blanking and rolling techniques.

Another object of the invention is a new method of production which is not only applicable to stainless steels but which also can be used with advantage for production from ordinary or normal steels, to give both increased strength and speed of production, and a generally improved appea-rance and better product.

The invention comprises the method of manufacture of a multi-pronged fork, or like pronged implement, for agricultural, horticultural and other purposes consisting inter alia in the steps of initial partial blanking so as to leave the prongs at least in pairs in integral mass formation, rolling such integral mass prong formations to produce the required dimensional taper followed by further 3,345,887 Patented Oct. 10, 1967 step of blanking to form the individual prongs from each such integral mass prong formation.

Preferably all the said mass formations are rolled simultaneously so that this can be effected after one reheating operation, it being understood that after each rolling or blanking operation it is necessary to re-heat the work to the accepted working temperature for the next operation; and thereby enable all such rolling to be effected in a single operation. Again, after such rolling operation, the symmetrical spread and lengthening of the integral prong mass formations aforesaid provides sufficient width of metal to enable a final blanking operation to be used for forming all the individual prongs therefrom in a single blanking operation.

In the accompanying drawings:

FIG. 1 shows diagrammatically in plan the product of a partial blanking operation for a 4-pronged border fork made in accordance with the present invention;

FIG. 2 shows the blank of FIG. 1 after shaping of the socket;

FIGS. 3 and 4 are plan and side elevation respectively showing the blank after rolling to produce the required tapered thickness and length;

FIG. 5 shows the blank of FIGS. 3 and 4 after reblanking to form the individual prongs;

FIG. 6 is a side elevation to show shaping of the prongs and socket;

FIGS. 7 and 8 show a modification as adopted for the production of relatively larger forks, such as digging forks.

As can be seen from the drawings the blank of FIG. 1 can be produced with a minimum loss of material since the socket part 10 of the next blank, cut from a strip,

' is a residue of the preceding blanking operation to form the integral prong masses 11 and 12; from each of which 2 prongs will ultimately be made.

In FIG. 2 the socket 10 has been shaped in known manner, the blank of FIG. 1 being re-heated immediately before it has had time to cool more than is unavoidable. A normal working temperature for the blanking or rolling of stainless steel is of the order of 900 C. to 1000 C. and during formation of the socket, the remainder of the blank with normal speedy and skillful manipulation, need not fall in temperature below say 750 C. or 800 C.

In FIGS. 3 and 4 the two prong masses 11 and 12 have been re-heated and rolled to the required taper which both lengthens and widens them while reducing the original thickness of inch to some inch taper to inch.

In FIG. 5 the blank has been reheated and submitted to a second blanking operation to form two prongs 13 from each prong mass, at the same time pointing them and shaping the whole article to the curvature as shown in elevation in FIG. 6.

The resultant final blank is then ready after hardening and tempering, for finishing and polishing to a higher finish and better appearance than is possible with any stainless steel casting, in addition to having much better strength and other characteristics required for a fork of this kind. In addition to the initial (heating for the first blanking operation there are therefore only 3 re-heating stages, and with the exception perhaps of the rather longer operation of forming the socket, there is no need for the temperature of the main part of the blank to fall below say 800 C. or perhaps 750 C. between each operation, using normal skill of manipulation before re-heating for the next and it has been found that stainless steel which would normally be selected as suitable for such a fork is able to withstand such cooling and re-heating and operational treatment without serious detriment to the nature of the metal. As compared with the bending and rebending to which the prongs are subjected in present known methods for the making of such a fork and the greater temperature changes which such prongs suffer during each operation owing to their relatively small mass, when they may cool to black heat around 500 C., the temperature changes are relatively small in the prongs produced by the steps above described, owing to the relatively large mass of the two-prong masses right up to the last blanking operation, which mass holds the heat and reduces the rate of cooling.

From an economic standpoint the parts removed in the final blanking operation for this size of fork can be used to produce smaller garden and other implements, so that the waste factor is reasonable.

For larger fork however, after rolling for taper, as shown in FIGS. 3 and 4 of the billet is reblanked twice, firstly as shown in FIG. 7 so that the main space 14- between the inner prongs 15 are at their intended final distance apart, as also in the first blanking operation. The integral prong masses however have their intended prongs relatively close together as can be seen from FIG. 8 after a further blanking operation which leaves outer prongs 16 longer than the inner prongs 15. The space between the prongs is only sufficient to enable such further blanking and to have enough heat-retaining mass for intermediate rolling operations. Thereafter, the outer prongs are square set to widen their spacing, and after a final stamping to contour, the fork is ready for hardening, tempering and finishing as in the example first described. Although additional re-heating is involved for the extra blanking operation and the square setting, such operations can again be performed under conditions which avoid excessive cooling up to the final stages of separating the prongs from their integral prong masses and giving them their final shape and in this way it has been found not only practical to use stainless steel but greatly to increase the rate of production and improve the quality of the product whether made of stainless or ordinary steel.

The invention is obviously not limited to all the details '4 of construction above described in so far as they may be modified without departing from the principles therein contained, in particular the integral prong mass formation of the blank in its early stage.

I claim:

1. A method of forming prongs of a multi-pronged fork for agricultural and horticultural purposes consisting essentially of partially blanking a stainless steel sheet so as to leave prongs at least in pairs in integral mass formations, heating said fork to working temperature, rolling said formations to produce the desired dimensional taper, heating said formations to working temperature, finally blanking said formations to form individual prongs having final desired dimensions from each of said formations, each of said formations consists of the combined width of the pair of prongs and a narrow strip between them, said formations constituting heat retaining masses whereby intermediate rolling operations can be performed without reheating.

2. A method according to claim 1 wherein said fork has four prongs and there are two of said formations, both of said formations being rolled simultaneously in a single operation, whereby the one final blanking produces prongs having desired dimensions.

3. A method according to claim 2 wherein said formations are reheated only twice.

References Cited UNITED STATES PATENTS 84,377 11/1868 Richardson 76-411 85,400 12/ 1868 Richardson 761 11 337,099 3/ 1886 Warner 7 6-105 406,480 7/ 1889 Silliman et al 76l 11 524,719 8/1894 Kretsinger 76-111 GRANVILLE Y. CUSTER, 111., Primary Examiner. 

1. A METHOD OF FORMING PRONGS OF A MULTI-PRONGED FORK FOR AGRICULTURAL AND HORTICULTURAL PURPOSES CONSISTING ESSENTIALLY OF PARTIALLY BLANKING A STAINLESS STEEL SHEET SO AS TO LEAVE PRONGS AT LEAST IN PAIRS IN INTEGRAL MASS FORMATIONS, HEATING SAID FORK TO WORKING TEMPERATURE, ROLLING SAID FORMATIONS TO PRODUCE THE DESIRED DIMENSIONAL TAPER, HEATING SAID FORMATIONS TO WORKING TEMPERATURE, FINALLY BLANKING SAID FORMATIONS TO FORM INDIVIDUAL PRONGS HAVING FINAL DESIRED DIMENSIONS FROM EACH OF SAID FORMATIONS, EACH OF SAID FORMATIONS CONSISTS OF THE COMBINED WIDTH OF THE PAIR OF PRONGS AND A NARROW STRIP BETWEEN THEM, SAID FORMATIONS CONSTITUTING HEAT RETAINING MASSES WHEREBY INTERMEDIATE ROLLING OPERATIONS CAN BE PERFORMED WITHOUT REHEATING. 